Lycopene crystalloids exhibit singlet exciton fission in tomatoes

2018 ◽  
Vol 20 (13) ◽  
pp. 8640-8646 ◽  
Author(s):  
M. J. Llansola-Portoles ◽  
K. Redeckas ◽  
S. Streckaité ◽  
C. Ilioaia ◽  
A. A. Pascal ◽  
...  
Keyword(s):  
Excited State ◽  
Transient Absorption ◽  
Singlet Exciton ◽  
Absorption Studies ◽  
Singlet Exciton Fission

Transient absorption studies conducted on in vitro lycopene aggregates, as well as on lycopene crystalloids inside tomato chromoplasts, reveal the appearance of a long-lived excited state, which we unambiguously identified as lycopene triplet generated by singlet exciton fission.

scholarly journals Ultrafast Exciton Dynamics in Two Dimensional Covalent Organic Frameworks Reveals Size Dependence to Exciton Diffusion

2020 ◽  
Author(s):  
Nathan C. Flanders ◽  
Matthew S. Kirschner ◽  
Pyosang Kim ◽  
Thomas Fauvell ◽  
Austin Evans ◽  
...  
Keyword(s):  
High Performance ◽  
Transient Absorption ◽  
Domain Size ◽  
Spectroscopic Techniques ◽  
Two Dimensional ◽  
Exciton Dynamics ◽  
Singlet Exciton ◽  
Exciton Diffusion ◽  
Absorption Studies ◽  
Exciton Annihilation

<p>Large singlet exciton diffusion lengths are a hallmark of high performance in organic based devices such as photovoltaics, chemical sensors, and photodetectors. In this study, exciton dynamics of a two-dimensional covalent organic framework, COF- 5, is investigated using ultrafast spectroscopic techniques. Following photoexcitation, the COF-5 exciton decays via three pathways: 1) excimer formation (4 ± 2 ps), 2) excimer relaxation (160 ± 40 ps), and 3) excimer decay (>3 ns). Excitation fluence-dependent transient absorption studies suggest that COF-5 has a relatively large diffusion coefficient (0.08 cm2/s). Furthermore, exciton-exciton annihilation processes are characterized as a function of COF-5 crystallite domain size in four different samples, which reveal domain- size dependent exciton diffusion kinetics. These results reveal that exciton diffusion in COF-5 is constrained by its crystalline domain size. These insights indicate the outstanding promise of delocalized excitonic processes available in 2D COFs, which motivate their continued design and implementation into optoelectronic devices. </p>

scholarly journals Singlet fission in thin films of metallo-supramolecular polymers with ditopic thiophene-bridged terpyridine ligands

2017 ◽  
Vol 5 (32) ◽  
pp. 8041-8051 ◽  
Author(s):  
David Rais ◽  
Jiří Pfleger ◽  
Miroslav Menšík ◽  
Alexander Zhigunov ◽  
Pavla Štenclová ◽  
...  
Keyword(s):  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Supramolecular Polymers ◽  
Uv Laser ◽  
Singlet Fission ◽  
Thin Solid Films ◽  
Singlet Exciton ◽  
Solid Films ◽  
Terpyridine Ligands ◽  
Singlet Exciton Fission

Ultrafast singlet exciton fission in thin solid films after UV laser photoexcitation was observed using transient absorption spectroscopy.

Transient absorption studies of the Ru(dcbpy)2(NCS)2 excited state and the dye cation on nanocrystalline TiO2 film

2001 ◽  
Vol 340 (3-4) ◽  
pp. 217-221 ◽  
Author(s):  
Jani Kallioinen ◽  
Viivi Lehtovuori ◽  
Pasi Myllyperkiö ◽  
Jouko Korppi-Tommola
Keyword(s):  
Excited State ◽  
Tio2 Film ◽  
Transient Absorption ◽  
Nanocrystalline Tio2 ◽  
Absorption Studies

Excited state electron transfer in A2 and A2B2 functionalized zinc porphyrins carrying rigid and flexible β-pyrrole π-extended substituents

2020 ◽  
Vol 24 (05n07) ◽  
pp. 904-919
Author(s):  
Michael B. Thomas ◽  
Siddhartha Kumar ◽  
Timothy Esquivel ◽  
Hong Wang ◽  
Francis D’Souza
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Transient Absorption ◽  
Binding Constants ◽  
Free Energy Calculations ◽  
Stable Complex ◽  
State Electron ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies ◽  
Zinc Porphyrins

Optical absorption and emission, electrochemical, and photochemical properties of peripherally functionalized with flexible and rigid [Formula: see text]-extended substituents on A2 and A2B2 type zinc porphyrins is investigated. The significance of rigid [Formula: see text]-substituents over flexible ones in governing the spectral properties is unraveled. Flexible [Formula: see text]-substituents on the porphyrin ring caused appreciable spectral broadening compared to porphyrin carrying rigid [Formula: see text]-substituents. Further, supramolecular dyads are formed by coordinating phenyl imidazole functionalized fullerene, C[Formula: see text]Im. The calculated binding constants for the 1:1 complexes is in the order of 2–7 × 105 M[Formula: see text] suggesting stable complex formation. Free-energy calculations performed according to the Rehm–Weller approach suggested possibility of excited state electron transfer in these dyads. Femtosecond transient absorption studies of the dyads performed in [Formula: see text]-dichlorobenzene showed evidence of occurrence of electron transfer from the singlet-excited state that was in competition with the intersystem crossing process to populate the triplet-excited state of porphyrins.

scholarly journals Strategies for Design of Potential Singlet Fission Chromophores Utilizing a Combination of Ground State and Excited State Aromaticity Rules

2020 ◽  
Author(s):  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Henrik Ottosson
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Geometric Model ◽  
Substituent Effects ◽  
Singlet Fission ◽  
Singlet Exciton ◽  
Singlet Exciton Fission ◽  
Homo Lumo ◽  
Potential Use

Singlet exciton fission photovoltaics requires chromophores with their lowest excited states arranged so that 2<i>E</i>(T<sub>1</sub>) < <i>E</i>(S<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) < <i>E</i>(T<sub>2</sub>). Herein, qualitative theory and quantum chemical calculations are used to develop explicit strategies on how to use Baird’s 4<i>n</i> rule on excited state aromaticity, combined with Hückel’s 4<i>n</i>+2 rule for ground state aromaticity, to tailor new potential chromophores for singlet fission. We first analyze the <i>E</i>(T<sub>1</sub>), <i>E</i>(S<sub>1</sub>) and <i>E</i>(T<sub>2</sub>) of benzene and cyclobutadiene (<b>CBD</b>) as, respectively, excited state antiaromatic and aromatic archetypes, and reveal that <b>CBD </b>fulfils the criteria on the state ordering for a singlet fission chromophore. We then look at fulvenes, a class of compounds that can be tuned by choice of substituents from Baird-antiaromatic to Baird-aromatic in T<sub>1</sub> and S<sub>1</sub>, and from Hückel-aromatic to Hückel-antiaromatic in S<sub>0</sub>. The T<sub>1</sub> and S<sub>1</sub> states of most substituted fulvenes (159 of 225) are described by singly excited HOMO→LUMO configurations, providing a rational for the simultaneous tuning of <i>E</i>(T<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) along an approximate (anti)aromaticity coordinate. Key to the tunability is the exchange integral (K<sub>H,L</sub>), which ideally is constant throughout the compound class, providing a constant D<i>E</i>(S<sub>1</sub>-T<sub>1</sub>). This leads us to a geometric model for identification of singlet fission chromophores, and we explore what factors limit the model. Candidates with calculated <i>E</i>(T<sub>1</sub>) of ~1 eV or higher are identified among benzannelated 4<i>n</i>pi-electron compound classes and siloles. In brief, it is clarified how the joint utilization of Baird’s 4<i>n</i> and Hückel’s 4<i>n</i>+2 rules, together with substituent effects (electronic and steric) and benzannelation, can be used to tailor new chromophores with potential use in singlet fission photovoltaics.<br>

scholarly journals Strategies for Design of Potential Singlet Fission Chromophores Utilizing a Combination of Ground State and Excited State Aromaticity Rules

2020 ◽  
Author(s):  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Henrik Ottosson
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Geometric Model ◽  
Substituent Effects ◽  
Singlet Fission ◽  
Singlet Exciton ◽  
Singlet Exciton Fission ◽  
Homo Lumo ◽  
Potential Use

Singlet exciton fission photovoltaics requires chromophores with their lowest excited states arranged so that 2<i>E</i>(T<sub>1</sub>) < <i>E</i>(S<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) < <i>E</i>(T<sub>2</sub>). Herein, qualitative theory and quantum chemical calculations are used to develop explicit strategies on how to use Baird’s 4<i>n</i> rule on excited state aromaticity, combined with Hückel’s 4<i>n</i>+2 rule for ground state aromaticity, to tailor new potential chromophores for singlet fission. We first analyze the <i>E</i>(T<sub>1</sub>), <i>E</i>(S<sub>1</sub>) and <i>E</i>(T<sub>2</sub>) of benzene and cyclobutadiene (<b>CBD</b>) as, respectively, excited state antiaromatic and aromatic archetypes, and reveal that <b>CBD </b>fulfils the criteria on the state ordering for a singlet fission chromophore. We then look at fulvenes, a class of compounds that can be tuned by choice of substituents from Baird-antiaromatic to Baird-aromatic in T<sub>1</sub> and S<sub>1</sub>, and from Hückel-aromatic to Hückel-antiaromatic in S<sub>0</sub>. The T<sub>1</sub> and S<sub>1</sub> states of most substituted fulvenes (159 of 225) are described by singly excited HOMO→LUMO configurations, providing a rational for the simultaneous tuning of <i>E</i>(T<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) along an approximate (anti)aromaticity coordinate. Key to the tunability is the exchange integral (K<sub>H,L</sub>), which ideally is constant throughout the compound class, providing a constant D<i>E</i>(S<sub>1</sub>-T<sub>1</sub>). This leads us to a geometric model for identification of singlet fission chromophores, and we explore what factors limit the model. Candidates with calculated <i>E</i>(T<sub>1</sub>) of ~1 eV or higher are identified among benzannelated 4<i>n</i>pi-electron compound classes and siloles. In brief, it is clarified how the joint utilization of Baird’s 4<i>n</i> and Hückel’s 4<i>n</i>+2 rules, together with substituent effects (electronic and steric) and benzannelation, can be used to tailor new chromophores with potential use in singlet fission photovoltaics.<br>

scholarly journals Ultrafast spectroscopy reveals singlet fission, ionization and excimer formation in perylene film

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenjun Ni ◽  
Licheng Sun ◽  
Gagik G. Gurzadyan
Keyword(s):  
Radical Cation ◽  
Transient Absorption ◽  
Photovoltaic Devices ◽  
Singlet Fission ◽  
Time Resolved ◽  
Singlet Exciton ◽  
Femtosecond Transient Absorption ◽  
Photovoltaic Applications ◽  
Singlet Exciton Fission ◽  
Triplet Formation

AbstractSinglet exciton fission (SF) is a spin-allowed process whereby two triplet excitons are created from one singlet exciton. This phenomenon can offset UV photon energy losses and enhance the overall efficiency in photovoltaic devices. For this purpose, it requires photostable commercially available SF materials. Excited state dynamics in pure perylene film, ease of commercial production, is studied by time-resolved fluorescence and femtosecond transient absorption techniques under different photoexcitation energies. In film, polycrystalline regions contain perylene in H-type aggregate form. SF takes place from higher excited states of these aggregates in ultrafast time scale < 30 fs, reaching a triplet formation quantum yield of 108%. Moreover, at λex = 450 nm singlet fission was detected as a result of two-quantum absorption. Other competing relaxation channels are excimer (1 ps) and dimer radical cation formation (< 30 fs). Excimer radiatively relaxes within 19 ns and radical cation recombines in 3.2 ns. Besides, exciton self-trapping by crystal lattice distortions occurs within hundreds of picosecond. Our results highlight potential of simple-fabricated perylene films with similar properties as high-cost single crystal in SF based photovoltaic applications.

Strategies for Design of Potential Singlet Fission Chromophores Utilizing Baird's Rule on Excited State Aromaticity

2019 ◽  
Author(s):  
Ouissam El Bakouri ◽  
Joshua R. Smith ◽  
Henrik Ottosson
Keyword(s):  
Excited State ◽  
Excited States ◽  
Geometric Model ◽  
Substituent Effects ◽  
Singlet Fission ◽  
Singlet Exciton ◽  
Technology Platforms ◽  
Singlet Exciton Fission ◽  
Homo Lumo ◽  
Potential Use

In singlet exciton fission one photon of light is used to create two excitons of triplet multiplicity. This process requires chromophores with their lowest excited states arranged so that 2<i>E</i>(T<sub>1</sub>) < <i>E</i>(S<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) < <i>E</i>(T<sub>2</sub>). To match different technology platforms there is a high need for new candidate chromophores with the desired excited state orderings. Herein, qualitative theory and quantum chemical calculations are used to develop explicit strategies on how to use Baird’s 4n rule on excited state aromaticity to tailor new potential chromophores for singlet fission. We first analyze the <i>E</i>(T<sub>1</sub>), <i>E</i>(S<sub>1</sub>) and <i>E</i>(T<sub>2</sub>) of benzene and cyclobutadiene (CBD) as, respectively, excited state antiaromatic and aromatic archetypes, and reveal that CBD fulfils the criteria on the state ordering for a singlet fission chromophore. We then look at fulvenes, a class of compounds that can be tuned from Baird-antiaromatic to Baird-aromatic in T<sub>1</sub> and S<sub>1</sub> by choice of substituents. The T<sub>1</sub> and S<sub>1</sub> states of fulvenes are both described by singly excited HOMO→LUMO configurations, which provides a rational for the simultaneous and similar tuning of <i>E</i>(T<sub>1</sub>) and <i>E</i>(S<sub>1</sub>) along an approximate (anti)aromaticity coordinate. This leads us to a geometric model for identification of singlet fission chromophores. Candidates with calculated <i>E</i>(T<sub>1</sub>) of ~1 eV or higher are also identified among benzannelated 4<i>n</i>pi-electron compound classes and among siloles influenced to various extents by Baird-(anti)aromaticity in T<sub>1</sub> and S<sub>1</sub>. Finally, we explore the limitations of the design approach. In brief, it is clarified how Baird’s 4<i>n</i> rule together with substituent effects (electronic and steric) and benzannelation can be used to tailor new chromophores with potential use in singlet fission photovoltaics. <br>

scholarly journals Ultrafast Exciton Dynamics in Two Dimensional Covalent Organic Frameworks Reveals Size Dependence to Exciton Diffusion

2020 ◽  
Author(s):  
Nathan C. Flanders ◽  
Matthew S. Kirschner ◽  
Pyosang Kim ◽  
Thomas Fauvell ◽  
Austin Evans ◽  
...  
Keyword(s):  
High Performance ◽  
Transient Absorption ◽  
Domain Size ◽  
Spectroscopic Techniques ◽  
Two Dimensional ◽  
Exciton Dynamics ◽  
Singlet Exciton ◽  
Exciton Diffusion ◽  
Absorption Studies ◽  
Exciton Annihilation

<p>Large singlet exciton diffusion lengths are a hallmark of high performance in organic based devices such as photovoltaics, chemical sensors, and photodetectors. In this study, exciton dynamics of a two-dimensional covalent organic framework, COF- 5, is investigated using ultrafast spectroscopic techniques. Following photoexcitation, the COF-5 exciton decays via three pathways: 1) excimer formation (4 ± 2 ps), 2) excimer relaxation (160 ± 40 ps), and 3) excimer decay (>3 ns). Excitation fluence-dependent transient absorption studies suggest that COF-5 has a relatively large diffusion coefficient (0.08 cm2/s). Furthermore, exciton-exciton annihilation processes are characterized as a function of COF-5 crystallite domain size in four different samples, which reveal domain- size dependent exciton diffusion kinetics. These results reveal that exciton diffusion in COF-5 is constrained by its crystalline domain size. These insights indicate the outstanding promise of delocalized excitonic processes available in 2D COFs, which motivate their continued design and implementation into optoelectronic devices. </p>

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